Closing in on dark matter
Dark-matter experiments hope to measure both the mass (x-axis) and interaction rate (y-axis) of WIMPs. From accelerator-based experiments we know that the mass must be at least 34 GeV c2. Supersymmetric theories predict that the interaction rate for the neutralino, one of the leading candidates for dark matter, is less than one event per kilogram of detector per day for a range of masses (pale green region). The first generation of detectors such as germanium ionization detectors (yellow line) were not sensitive enough to detect these low interaction rates. Subsequent generations of sodium-iodide (NaI) detectors have been more sensitive (blue and green lines), and experiments by the DAMA collaboration have detected so-called anomalous events (red rectangle) that might be dark-matter particles but may be caused by other interactions. The current sensitivity of the UKDMC NaI detectors (red line) and the predicted sensitivities of the next generation of UKDMC detectors (dark green region) are also shown.